Solid-state solar paint

ABSTRACT

Methods and devices for forming painted circuits using multiple layers of electrically conductive paint. In one aspect, a painted circuit includes a substrate and one or more paint layers applied to the substrate where the one or more paint layers each form an electrical component of the painted circuit, and where the one or more paint layers includes a p-type hole conducting paint layer applied to the substrate, a photosensitized paint layer applied to the p-type hole conducing paint layer, an n-type electron conducting paint layer applied to the photosensitized paint layer, and a transparent protective paint layer applied to the n-type electron conducting paint layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(e) of U.S.Patent Application No. 62/558,579, entitled “PAINT CIRCUITS,” filed Sep.14, 2017. The disclosure of the foregoing application is incorporatedherein by reference in its entirety for all purposes.

BACKGROUND

Traditional solar cells use substrates with highly regular crystallinestructure, for example, crystalline silicon. Newer technologies includethin-film, amorphous solar cells to create discrete layers of individualmaterial with highly regular and predictable chemical structure.Commercial solar cell fabrication, in general, requires highlyspecialized equipment, which restricts fabricated solar cells togeographic locations with access to the complex manufacturing equipmentand/or specialized shipping and installation capabilities.

SUMMARY

This specification relates to paint circuits that can be formed usingmultiple layers of electrically conductive paint, and can, for example,be used to form a solar paint circuit to convert sunlight intoelectricity.

In general, one innovative aspect of the subject matter described inthis specification can be embodied in a painted circuit including asubstrate and one or more paint layers applied to the substrate wherethe one or more paint layers each form an electrical component of thepainted circuit. The one or more paint layers of the painted circuitsincludes a p-type hole conducting paint layer applied to the substrate,a photosensitized paint layer applied to the p-type hole conducing paintlayer, an n-type electron conducting paint layer applied to thephotosensitized paint layer, and a transparent protective paint layerapplied to the n-type electron conducting paint layer. A paint layer ofthe one or more paint layers includes a conductive paint formulationhaving a resistance that is defined in part by a resistivity of aconductive material that is included in the conductive paint formulationand a thickness of the given paint layer, and where the resistance ofthe conductive paint formulation including a conductive material havinga higher resistivity provides a higher resistance than the resistance ofthe conductive paint formulation including a conductive material with alower resistivity.

These and other embodiments can each optionally include one or more ofthe following features. In some implementations, the p-type holeconducting paint layer includes p-type nanoparticles (e.g., copper oxidenanoparticles).

In some implementations, the photosensitized paint layer includes asemiconductor paint layer (e.g., titanium dioxide nanoparticles) and aphotosensitized dye paint layer (e.g., copper phthalocyanine).

In some implementations, the n-type electron conducting paint layerincludes n-type nanoparticles (e.g., aluminum-doped zinc oxidenanoparticles).

In some implementations, the painted circuit includes two or morecontacts, where each contact includes a metallic foil affixed to asubstrate or an n-type electron conducting paint layer and in electricalcontact with the substrate or the n-type electron conducting paintlayer, respectively.

In general, another aspect of the subject matter described in thisspecification can be embodied in methods that include a process formanufacturing a painted circuit including providing a substrate andapplying one or more paint layers on a surface of the substrate, wherethe one or more paint layers each forms an electrical component of thepainted circuit. Applying the one or more paint layers includes applyinga p-type hole conducting paint layer to the substrate to yield a layerof the p-type hole conducting paint in direct contact with thesubstrate, applying a photosensitized paint to the p-type holeconducting paint layer to yield a layer of the photosensitized paint indirect contact with the p-type hole conducting layer, applying an n-typeelectron conducting paint to the photosensitized paint layer to yield alayer of the n-type electron conducting paint in direct contact with thephotosensitized paint layer, and applying a transparent protective paintto the n-type electron conducting paint layer to yield a layer of thetransparent protective paint in direct contact with the n-type electronconducting paint layer, where a first paint layer of the one or morepaint layers includes a conductive paint formulation having a resistancethat is defined in part by a resistivity of a conductive material thatis included in the conductive paint formulation and a thickness of thegiven paint layer, and where the resistance of the conductive paintformulation including a conductive material having a higher resistivityprovides a higher resistance than the resistance of the conductive paintformulation including a conductive material with a lower resistivity.

In some implementations, applying a p-type hole conducting paintincludes applying a layer of p-type nanoparticles (e.g., copper oxidenanoparticles) dispersed in solution (e.g., deionized water and asurfactant) on to the substrate and sintering (e.g., photonic sintering)the p-type nanoparticles to form an electrically continuous p-type holeconducting paint layer.

In some implementations, applying a photosensitized paint includesapplying a layer of semiconductor paint including semiconductornanoparticles (e.g., titanium dioxide nanoparticles) dispersed insolution (e.g., deionized water and surfactant) on the p-type holeconducting paint layer and sintering (e.g., photonic sintering) thesemiconductor nanoparticles to form an electrically continuoussemiconductor paint layer. A layer of photosensitized dye paint (e.g.,copper phthalocyanine dispersed in a denatured alcohol) is applied tothe semiconductor paint layer and thermally processed (e.g., photoniccuring) to chemisorb the photosensitized dye paint layer onto thesemiconductor paint layer.

In some implementations, applying an n-type electron conducting paintincludes applying a layer of n-type nanoparticles (e.g., aluminum-dopedzinc oxide nanoparticles) dispersed in solution (e.g., deionized waterand surfactant) on the photosensitized paint layer and sintering (e.g.,photonic sintering) the n-type nanoparticles to form an electricallycontinuous n-type electron conducting paint layer.

In some implementations, the painted circuit is thermally processed(e.g., by photonic curing). The thermal processing of the paintedcircuit may be done after all of the paint layers are applied to thepainted circuit. In some implementations, the thermal processing is doneprior to applying a transparent protective coating to the paintedcircuit (e.g., applying the transparent protective coating to the n-typeelectron conducting paint layer). Thermal processing of the paintedcircuit may be done after applying the transparent protective coating tothe painted circuit.

Particular embodiments of the subject matter described in thisspecification can be implemented to realize one or more of the followingadvantages. Unlike traditional commercial solar cell fabrication, solarpaint circuits can be fabricated with few tools (e.g., a hand mixer andan aerosolized sprayer) by individuals in any location (e.g., even inremote regions that do not have access to electricity or other resourcesrequired by conventional approaches). The solar paint circuits discussedherein are created using combinations of basic, inexpensive materials toform electronic circuits, which reduces fabrication complexity andreduces the cost to the manufacturer and end-user. In general, many ofthe materials used in the solar paint circuits are less hazardous andare less expensive to manufacture and ship than materials used intraditional solar cells. The paint circuits described here have areduced upfront capital expenditure requirement relative to traditionalcircuit fabrication and can be fabricated on-site as result, reducingimport/export tax or customs duty in countries where traditional circuitfabrication facilities cannot be established. Additionally, existinginfrastructure in commonly found paint factories can be converted easilyto produce solar paint circuits, whereas traditional solar cellfabrication requires highly specialized equipment. The relationshipbetween the electrically active material and its paint substrate enablethe electrical properties of the paint to be selected using relativelysimple mathematical analyses. Additionally, the ability to control theviscosity of the paint and/or the number of layers applied enables theelectrical characteristics to be easily changed by changing theviscosity and/or the number of layers of paint applied. This type offlexibility is typically unavailable with more conventional,high-precision circuit fabrication methods.

The details of one or more embodiments of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages of thesubject matter will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example solar paint circuit.

FIG. 2 is a flow chart of an example process for producing solar paint.

FIG. 3 is a flow chart of another example process for producing solarpaint.

FIG. 4 is a flow chart of another example process for producing solarpaint.

FIG. 5 is a flow chart of an example process for painting a solar paintcircuit.

FIG. 6 is a flow chart of another example process for painting a solarpaint circuit.

FIG. 7 is a flow chart of an example process for painting a p-type holeconducting paint layer.

FIG. 8 is a flow chart of an example process for painting aphotosensitized paint layer.

FIG. 9 is a flow chart of an example process for painting an n-typeelectron conducting paint layer.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

Overview

Described below are devices, systems, and methods for producing solarpaint and solar paint circuits. A paint circuit (e.g., a solar paintcircuit) is created through a layer-by-layer application of electricallyconductive paint (e.g., solar paint) to a surface of a substrate. Thesubstrate can be, for example, a piece of wood, brick, plaster, stone,metal surface, or another surface to which paint can be applied. Theapplication of layers of solar paint to the substrate can be done byhand using an aerosol dispenser or other aerosolized spray tool.

Though the term “solar paint circuit,” and “solar paint” are used in thecontext of describing particular embodiments of the subject matter, itis not meant to be limiting. Other paint circuits can be implementedwhich do not integrate solar energy (e.g., a battery, a light-emittingdiode, an antenna, or other circuit elements), as well as paint layersthat are not directly involved in forming solar-integrating circuits.

In some implementations, a painted circuit can be created by applying asingle paint layer to a substrate. For example, a simple resistivecircuit can be created by applying a single paint layer to thesubstrate. As discussed in more detail below, the paint layer applied tothe substrate can be a conductive paint formulation having a resistancethat is defined in part by a resistivity of a conductive material thatis included in the conductive paint formulation and thickness of thepaint layer. In some implementations, when conductive material withhigher resistivity is included in the paint formulation, the resistanceof the paint formulation will be higher than when conductive materialwith lower resistivity is included in the paint formulation.

In some implementations, a paint layer is applied through a template(e.g., a mask, stencil, and/or screen printing tool), such that paint isapplied to a substrate in a portion of the template but is preventedfrom being applied to the substrate in a second, different portion ofthe template.

In some implementations, a paint layer can be applied using a paintbrush, paint roller, or other painting tool. Paint for a paint layer canbe aerosolized and applied to a substrate using an aerosol spray tool,spray can, or other aerosol dispensers.

In some implementations, multiple paint layers are applied to thesubstrate to create a painted circuit. For example, after a first layerof paint is applied to the portion of the substrate, other layers can beapplied to other portions of the substrate (e.g., adjacent to the firstlayer) and/or applied to already painted portions of the substrate(e.g., applied over the first layer of paint). Each layer of paint formsan electrical component of the painted circuit (e.g., an electrontransport layer, a hole transport layer, etc.).

A paint layer can include a conductive paint formulation where aresistance of the paint layer is defined in part by a resistivity of aconductive material that is included in the conductive paint formulationand a thickness of the given paint layer, and where the resistance ofthe conductive paint formulation including a conductive material havinga higher resistivity provides a higher resistance than the resistance ofthe conductive paint formulation including a conductive material with alower resistivity.

Adjusting a viscosity of the paint layer can change a thickness of thepaint layer applied to the substrate, which in turn will affect theresistance of the paint layer. For example, a paint formulation with ahigher viscosity will result in a thicker paint layer than a paintformulation with a lower viscosity, and thicker layers of paint willgenerally have higher resistance in a direction perpendicular to theplane of the layer than thinner layers of similar formulation.

In some implementations, a droplet size of a paint dispersed by anaerosolized sprayer determines, in part, a thickness of the paint layerapplied to the substrate, which in turn will affect theresistance/conductance of the paint layer. For example, a larger dropletsize of a paint dispensed by an aerosolized sprayer will result in athicker paint layer than a smaller droplet size of the same paintdispensed by the aerosolized sprayer, and thicker layers of paint willgenerally have higher resistance in a direction perpendicular to theplane of the layer than thinner layers of similar formulation.

In some implementations, one or more paint layers can be sintered toyield structural and/or electrical properties of the one or more paintlayers. Sintering of paint layers which include one or morenanomaterials (e.g., nanoparticles) can, for example, causedensification of the paint layers by agglomeration, reduction ofporosity, and/or grain growth. Sintering of paint layers can beperformed using, for example, a furnace, a rapid thermal processingsystem, a high-powered lamp (e.g., photonic sintering), or other systemthat provides elevated temperatures for a duration of a sinteringprocess.

Various types of circuits and devices can be fabricated using solarpaint including a solar cell described below. Other solar paint circuitscan be created using the techniques described below, including a solarbattery, where a solar cell charges a battery. Another example of asolar paint circuit is a solar-powered streetlight, including a solarcell, a battery, and a light-emitting circuit. Another example of asolar paint circuit is a solar cell including an output regulator toregulate the solar cell to a maximum power point of the solar cell,which can be used as part of a cell phone charging circuit. Variouscircuit elements, such as resistors, capacitors, diodes, andtransistors, can be fabricated using the solar paint described herein.

Though the example circuit described below is depicted in block diagramform as single layers of each respective paint layer, multipleapplications (e.g., multiple layers) of particular paint layers can beused to achieve desirable electrical and/or functional properties.Additionally, though the example depicted below describes a singlesub-circuit (e.g., a single solar cell) integrated and/or painted on onepaint circuit, multiple sub-circuits may be incorporated and/or paintedto form a larger paint circuit (e.g., multiple solar cells) to achievedesired device performance).

Example Solar Paint Circuit

FIG. 1 is a block diagram of an example solar paint circuit 100. Thesolar paint circuit 100 includes a substrate 102, a p-type holeconducting paint layer 104, a photosensitized paint layer 106, an n-typeelectron conducting paint layer 108, and a transparent protective paintlayer 110. In some implementations, the solar paint circuit 100 is asolar cell. A solar cell is an electrical device that converts theenergy of light (e.g., sunlight) into electricity. Photons (e.g.,sunlight) are absorbed in the photosensitized paint layer 106, andcharge generation of electrons and holes occurs. The generated chargesare then separated and the electrons move towards the cathode and holesmove towards the anode, respectively, to generate electricity.

The p-type hole conducting paint layer 104 can be created by applying ap-type hole conducting paint to at least a portion of the substrate 102(e.g., a surface composed of wood, metal, plaster, stone, brick, oranother paintable material). In some implementations, the p-type holeconducting paint layer 104 forms an anode for the solar paint circuit100. The p-type hole conducting paint layer 104 can be formed by anaqueous paint composition including p-type nanomaterials dispersed in asolution. Formulations for the p-type hole conducting paint layer 104are discussed in further detail below.

The photosensitized paint layer 106 forms a layer where photons can beabsorbed and charge generation takes place in the solar paint circuit100. The photosensitized paint layer 106 can be formed from paintcompositions including an electron acceptor, a dye, and a solution. Thephotosensitized paint layer 106 is depicted as a single functional layerin solar paint circuit 100, however, it can be created by applying twoor more different paint layers including a semiconductor paint layerhaving an electron acceptor material and a photosensitized dye paintlayer. Formulations for the photosensitized paint layer 106 includingformulations for a semiconductor paint layer and a photosensitized dyepaint layer are discussed in further detail below.

The n-type electron conducting paint layer 108 is applied to thephotosensitized paint layer 106. In some implementations, the n-typeelectron conducting paint layer 108 forms a cathode for solar paintcircuit 100. The n-type electron conducting paint layer 108 can beformed by an aqueous paint composition including n-type nanomaterialsdispersed in a solution. The n-type electron conducting paint layer 108can be transparent or semi-transparent to allow light to reach thephotosensitized paint layer 106 below. In some implementations, ratherthan an n-type electron conducting paint layer 108, an electricallyconductive mesh (e.g., a wire mesh) is used as a cathode layer for solarpaint circuit 100.

A transparent protective paint layer 110 is applied to the n-typeelectron conducting layer 108. The transparent protective paint layer110 can be a transparent protecting coating and can be electricallyinsulating (e.g., laminate, polyurethane finish, shellac). In someimplementations, the transparent protective paint layer 110 encapsulatesa portion or all of the exposed surfaces of the solar paint circuit 100.The transparent protective paint layer 110 forms a protective layer overpart or all of the solar paint circuit 100 to protect the solar paintcircuit 100 paint layers from environmental effects (e.g., UV radiation,weather, water/humidity). In some implementations, the transparentprotective paint layer 110 is semi-transparent, and/or only transparentto certain wavelengths ranges (e.g., transparent to visiblewavelengths). In some implementations, the transparent protective paintlayer 110 is omitted, depending in part on application and/orenvironmental factors (e.g., level of exposure to weather). When thetransparent protective paint layer 110 is omitted, the n-type electronconducting paint layer 108 can function as a conductive protective layer(e.g., indium tin oxide).

The solar paint circuit 100 operates to absorb photons from the ambientenvironment (e.g., solar rays) in the photosensitized paint layer 106,such that electron-hole pairs are formed within the photosensitizedpaint layer 106, and charge separation occurs between the p-type holeconducting paint layer 104 and the n-type electron conducting paintlayer 108.

In some implementations, the separated charges from solar paint circuit100 are then used to charge (e.g., trickle charge) a battery. The solarpaint circuit 100 can be combined with other circuit elements to producea solar-powered light (e.g., a solar-powered streetlight). For example,the solar paint circuit 100 may be combined with a solar battery and alight-emitting circuit, where the solar paint circuit 100 can be used togenerate electricity from sunlight to charge (e.g., trickle charge) asolar battery, which can then be used to power a light-emitting circuit.The powered light-emitting circuit can then emit light in a particularrange of wavelengths (e.g., visible light).

In some implementations, multiple solar paint circuits 100 are connectedtogether in series. Connecting multiple solar paint circuits 100together in series can increase the amount of electricity generated andavailable to power another circuit (e.g., a light-emitting circuit, acell phone device, etc.) or charge a solar battery.

In some implementations, multiple solar paint circuits are electricallyconnected together to form larger systems of circuits. The multiplesolar paint circuits can be of a same or of different types, and can beconnected together in series and/or in parallel, depending onfunctionality of the larger system. For example, multiple solar cellscan be connected in series to one or more solar batteries such thatmultiple solar cells can be used to charge a solar battery, increasingthroughput.

In some implementations, electrical contacts 112 can be included in thesolar paint circuit 100. The electrical contacts can include a firstcontact (e.g., metallic foil, metallic mesh, cold weld bonding compound,solder ball, alligator clip, or the like) affixed to an n-type electronconducting paint layer 108 or to a substrate 102. A second contact(e.g., metallic foil, metallic mesh, cold weld bonding compound, solderball, alligator clip, or the like) can be affixed to a p-type holeconducting paint layer 104. The electrical contacts can be used toconnect to the solar paint circuit 100 to an external device (e.g., amobile phone, computer, or other battery-operated device). Theelectrical contacts 112 can also be used to connect the solar paintcircuit 100 to other solar circuits, for example, to daisy-chain a setof solar cell painted circuits, to increase throughput for poweringand/or charging a user device (e.g., a cell phone or computer), orcharging a solar battery.

Example Process for Producing Solar Paint Formulations

Solar paint circuits, including the solar paint circuit 100 describedherein with reference to FIG. 1, include multiple layers of solar paint.Solar paint can include various formulations selected to give the solarpaint layers applied with the particular solar paint differentelectrical (e.g., resistive/conductive), reactive (e.g.,photo-reactive), dielectric (e.g., voltage breakdown) and physicalproperties (e.g., viscosity). In some implementations, paintformulations are aqueous and include water, a solvent (e.g., ethanol),and/or an emulsifier.

In some implementations, paint formulations include nanoparticles (e.g.,metallic or semiconductor nanoparticles) dispersed in a solution (e.g.,ethanol, deionized water and surfactant).

Implementations of solar paints include conductive paint (e.g., forn-type electron conducting and p-type hole conducting paint layers).Conductive paint can be an aqueous composition including one or moreconductive or semiconductor nanomaterials (e.g., metallic orsemiconductor nanoparticles) dispersed in solution. Examples of suitablenanomaterials include aluminum-doped zinc oxide nanoparticles, copperoxide nanoparticles, and carbon-based nanomaterials (e.g., carbonnanotubes). Examples of suitable solution include deionized water with adispersant (e.g., benzenesulfonic acid or sodium dodecyl sulfate) anddenatured alcohol (e.g., denatured ethanol). In some implementations,conductive nanomaterials (e.g., nanoparticles) are selected based inpart on a transparency of the resulting conductive paint including theconductive nanomaterials. Additionally, deflocculants (e.g., sodiumlauryl dodecasulfide or a basic salt like sodium carbonate or potassiumcarbonate) can be added to the conductive paint including the conductingnanomaterials to prevent flocculation, minimize surface energy of thedispersed nanoparticles, and assist in dispersion of the nanomaterialsand improve transparency.

In some implementations, the conductive paint is treated in anultrasonic bath to break up aggregated nanomaterials and filtered (e.g.,through a microfiber cloth) in order to fully disperse the nanomaterialsin the conductive paint. In some implementations, the conductive paintmay be dispersed using a ball mill treatment and/or high-shear mixing.

FIG. 2 is a flow chart of an example process for producing solar paint.Referring to FIG. 2, conductive paint can be prepared by process 200. In202, a suitable conductive material is dispersed in solution to yieldthe conductive paint. For example, a conductive material (e.g.,aluminum-doped zinc oxide nanoparticles) may be dispersed in solvent(e.g., ethanol) to yield a conductive paint. In 204, the conductivepaint can optionally be agitated (e.g., in an ultrasonic bath orstirred) and filtered (e.g., through a microfiber cloth) to evenlydisperse the nanomaterial in the solution.

Conductive paints prepared according to the process of FIG. 2 caninclude n-type semiconductor materials as the conductive material, e.g.,for use as an n-type electron conducting paint layer 108. Examples ofn-type semiconductor materials include carbon-based materials, such asgraphite powder, activated charcoal, and n-type carbon nanomaterialssuch as nanoparticles or nanotubes. The n-type semiconductor materialscan be doped with an n-type dopant, such as nitrogen, to reduce the workfunction of the semiconductor material, thus decreasing the forwardvoltage drop of the diode. For instance, graphite powder having adiameter of 50-800 μm can be used.

In some implementations, n-type semiconductor materials includealuminum-doped zinc oxide (AZO) nanoparticles dispersed in deionizedwater. For example, a ratio of AZO nanoparticles dispersed in deionizedwater can be 1:50. Nanoparticle size distribution in the n-typesemiconductor material may depend, in part, on cost considerationsrelated to generating the n-type electron conducting paint. Nanoparticlesize distribution can be selected to optimize light absorption andminimize light scattering for a particular solar spectrum (e.g., AM1.5G) within the paint layer including the nanoparticles.

Conductive paints prepared according to the process FIG. 2 can includep-type semiconductor materials as the conductive material, e.g., for useas a p-type hole conducting paint layer. Examples of p-typesemiconductor materials include p-type hole-conducting nanomaterials(e.g., copper(II) oxide nanoparticles, copper(I) oxide nanoparticles,and nickel(II) oxide nanoparticles). In some examples, a dispersantmaterial, such as benzenesulfonic acid or sodium dodecyl sulfate, can beadded to the water phase of the conductive paint to facilitatedispersion of the p-type semiconductor material in the water.

In some implementations, a p-type semiconductor material includes copperoxide nanoparticles dispersed in solvent in a 1:1 ratio. Nanoparticlesize distribution in the p-type semiconductor material may depend, inpart, on cost considerations related to the p-type hole conductingpaint. Nanoparticle size distribution can range from tens of nanometersto several micrometers in diameter and can be selected to optimize lightabsorption and minimize light scattering for a particular solar spectrum(e.g., AM 1.5G) within the paint layer including the nanoparticles, fora solar paint circuit where the p-type semiconductor material istransparent. In some implementations, paint layers including the p-typesemiconductor material are not transparent.

Implementations of solar paints can also include semiconductor paint andphotosensitized dye paint. In some implementations, photosensitizingpaint layers can combine two or more paint formulations including asemiconductor paint and a photosensitized dye paint to form thephotosensitized paint layer, discussed below in more detail withreference to FIG. 8.

Semiconductor paint can include an electron acceptor and a solution fordispersing the electron acceptor. Electron acceptors for a particularsemiconductor paint layer can be selected, in part, based on aninjection efficiency of the electron acceptor relative to aphotosensitizer used in the particular photosensitized dye paint layer.Examples of suitable electron acceptors include titanium dioxide (e.g.,rutile or anatase titanium dioxide nanoparticles), zinc oxide,benzothiadiazole, benzotriazole, quinoxaline, phthalimide,diketopyrrolopyrrole, thienopyrazine, thiazole, triazine, cyanovinyl,cyano- and fluoro-substituted phenyl, iodine, rhodanine, naphthalamide,and acrylic acids. In one example, titanium dioxide nanoparticles may beused as electron acceptors in a semiconductor paint. Size distributionof the titanium dioxide nanoparticles may depend, for example, on thedesired surface area of the nanoparticles, moiety of the semiconductorpaint, and thermodynamic stability of the semiconductor paint layer.

Various different dyes can be used to create photosensitized dye paint.Selection of the dyes used to create photosensitized dye paint candepend in part on an optimal absorption spectrum (e.g., within aspecified range) for a particular application (e.g., tropical vs. arcticlatitude, indoor vs. outdoor use). Additionally, a photosensitized dyepaint can include one or more different dyes for multiple-peakabsorption spectra functionality. In some implementations, the dye hashigh absorption (e.g., in the 500 nm range, which corresponds to a darkbluish-green color), and has at least one chromophore (functional groupwhich is the source of the color/photoactive response) which undergoesexcitation from a p to a p* highest-occupied molecular orbital (HOMO) onillumination. Examples of suitable dyes include copper phthalocyanine,zinc phthalocyanine, merocyanine, ruthenium-polypyridine, ironhexacyanoferrate, Ru-polypyridyl-complex sensitizers (e.g.,cis-dithiocyanato bis(4,4′-dicarboxy-2,2′-bipyridine)ruthenium(II)).

FIG. 3 is a flow chart of another example process for producing solarpaint. Referring to FIG. 3, a semiconductor paint can be prepared byprocess 300. In 302, semiconductor nanomaterial (e.g., titanium dioxidenanoparticles) is dispersed in a solution (e.g., denatured alcohol ordeionized water and a surfactant) to yield a semiconductor paint. In304, the semiconductor paint can optionally be agitated (e.g., in anultrasonic bath or stirred) and filtered (e.g., through a microfibercloth) to evenly disperse the semiconductor nanomaterial in thesolution.

FIG. 4 is a flow chart of another example process for producing solarpaint. Referring to FIG. 4, photosensitizing paint can be prepared byprocess 400. In 402, a suitable dye is combined with solvent (e.g.,denatured alcohol) to yield a photosensitizing paint. In one example, aphotosensitizing paint includes copper phthalocyanine in a weight ratioof anhydrous ethanol:copper phthalocyanine of 1:1.

Example Process for Producing Solar Paint Circuit

FIG. 5 is a flow chart of an example process 500 for painting a solarpaint circuit. In general, a solar paint circuit (e.g., solar paintcircuit 100) can be fabricated according to process 500, as shown in theflow diagram in FIG. 5. In 502, a substrate is provided. Substrates caninclude metal, wood, plaster, fabric, or the like. A substrate canfurther include a wire mesh or foil affixed to a base structuralmaterial, to provide electrical conductivity. In 504, one or more paintlayers are applied to a surface of the substrate, where each paint layerincludes a conductive paint formulation. In some implementations, eachapplied paint layer is allowed to dry prior to the application of asubsequent layer. In some implementations, each applied paint layer mayinclude a formulation having one or more solvents that are allowed toevaporate prior to the application of a subsequent layer.

A conductive paint layer applied using the conductive paint formulationhas a resistance defined, in part, by the resistivity of the conductivematerial included in the conductive paint formulation. For example, aconductive paint layer applied using conductive paint formulationincluding a first conductive material (e.g., a conductive nanomaterial)having a higher resistivity provides a higher resistance than aconductive paint layer applied using a conductive paint formulationincluding a second different conductive material having a lowerresistivity.

In some implementations, multiple coatings of a same conductive paintformulation can be applied to form a layer of a desired thickness, wherethe desired thickness is greater than a thickness of a single appliedlayer. Each coating of the same conductive paint may be allowed to dryprior to the application of a subsequent layer.

In some implementations, one or more dimensions of the substrate (e.g.,aluminum foil) are selected to maximize charge mobility and/or for easeof manufacturing of the solar paint circuit (e.g., roll-to-rollprocessing). Paint layers may be applied to a roughened surface of thealuminum foil to improve adhesion of the paint to the substrate,maximize a number of charge carriers available at the substrate surface,and/or increase the surface area of the substrate in contact with theapplied paint layers. In one example, a substrate is a long thin stripof aluminum foil.

In some implementations, one or more dimensions of the substrate (e.g.,aluminum foil) are selected to optimize a cost-per-power-output for thesolar paint circuit (e.g., solar cell) efficiency. Though the term“optimize” is used here in reference to a particular scenario where acost-per-power output is minimized, other “optimized” scenarios may bepossible depending on a desired outcome (e.g., low environmental impact,accessibility of materials, minimal manufacturing steps, etc.). Thus,the use of the terms “optimize,” “optimal,” or other similar terms asused herein do not refer to a single optimal outcome.

In one example of a solar cell design that is optimized forcost-per-power output and for a selected length of the solar cell (e.g.,selected based on a manufacturing process or dimensions of aninstallation location), a width of the solar cell can be determinedusing the following procedure. In this example, it is assumed that asolar cell manufactured with these specifications is used in consistentambient conditions (e.g., a regular amount of absorbable light energyand spectral distribution of the light energy). It is also assumed thata dominant source of shunt resistance is a transparent outer conductivelayer (e.g., n-type electron conducting layer) of the solar cell, forexample, that an electrode connecting the solar cell to an externalcircuit is highly conductive.

A width-independent photoconversion efficiency can be determined for asolar cell, where the solar cell includes an electrical contact with atop shunt electrode that is consistent along a length of the cell andlocated on one side of the solar cell, by covering the solar cell withan opaque barrier parallel to the top shunt electrode and measuring thepower output per unit of expose surface area for the solar cell.Dividing the power output per unit of exposed surface area by an inputenergy (I_(in)) in units of power per surface area (e.g., watts persquare meter) yields the solar cell efficiency. Width-independentphotoconversion efficiencies (e) can be found for multiple solar cellseach having different widths and a simple linear regression (e.g.,e_(total)=e_(wi)−we_(loss)) can be used to determine the power loss perunit of width (w) such that a y-intercept of the linear regression is awidth-independent photoconversion efficiency of the solar cell (ew_(i)).

For a selected length of solar cell (e.g., selected based on amanufacturing process or dimensions of an installation location), aknown cost per unit area (c_(area)), and a known cost per unit area ofthe electrodes (c_(electrode)), a solar cell width to optimize the costper power output (C_(power)) of the solar cell can be determined by aratio of the solar cell cost (C_(cell)) to the solar cell power output(I_(out)).

$\begin{matrix}{{C_{cell}(w)} = {{wlc}_{area} + {lc}_{electrode}}} & (1) \\{{I_{out}(w)} = {{I_{in}{wle}_{wi}} - {I_{in}{we}_{loss}}}} & (2) \\{{C_{power}(w)} = \frac{C_{cell}(w)}{I_{out}(w)}} & (3) \\{{C_{power}(w)} = \frac{{wlc}_{area} + {lc}_{electrode}}{{I_{in}{wle}_{wi}} - {I_{in}{we}_{loss}}}} & (4)\end{matrix}$

The derivatives of C_(cell)(w) and I_(out)(w) can be found.

C _(cell)′(w)=lc _(area)   (5)

I _(out)′(w)=I _(in) le _(wi) −I _(in) e _(loss)   (6)

C_(power)′(w) can be solved algebraically for positive, real values ofC_(power)′(w)=0, by substituting the known values of the constants tofind the optimal solar cell width.

$\begin{matrix}{{C_{power}^{\prime}(w)} = \frac{{{C_{cell}^{\prime}(w)}{I_{out}(w)}} - {{C_{cell}(w)}{I_{out}^{\prime}(w)}}}{I_{out}^{2}(w)}} & (7) \\{{C_{power}^{\prime}(w)} = \frac{\begin{matrix}{{\left( {lc}_{area} \right)\left( {{I_{in}{wle}_{wi}} - {I_{in}{we}_{loss}}} \right)} -} \\{\left( {{wlc}_{area} + {lc}_{electrode}} \right)\left( {{I_{in}{le}_{wi}} - {I_{in}e_{loss}}} \right)}\end{matrix}}{\left( {{I_{in}{wle}_{wi}} - {I_{in}{we}_{loss}}} \right)^{2}}} & (8)\end{matrix}$

FIG. 6 is a flow chart of another example process 600 for painting asolar paint circuit. Referring to FIG. 6, a solar paint circuit (e.g.,solar paint circuit 100) can be fabricated according to process 600.Substrates can be electrically conducting or electricallynon-conducting. Suitable electrically insulating substrates includewood, plaster, and plastic. Electrically conducting substrates caninclude substrates having relatively low work-function, low financialcost, low susceptibility to oxidation, and high physical strengthrelative to the one or more paint layers. Suitable electricallyconducting substrates include aluminum mesh, aluminum foil, as well aszinc, magnesium, nickel, copper, silver, gold, and platinum.

In 602, p-type hole conducting paint is applied to a substrate andallowed to dry to yield a layer of the p-type hole conducting paint indirect contact with the substrate. In some implementations, one or moreadditional layers of the p-type hole conducting paint can besubsequently applied. In some implementations, the one or more layers ofp-type hole conducting paint are subsequently sintered. The sinteringprocess for the one or more p-type hole conducting paint layers isdiscussed in more detail below with reference to FIG. 7.

In 604, photosensitizing paint is applied to the to the p-type holeconducting paint layer and allowed to dry to yield a layer of thephotosensitizing paint in direct contact with the layer of the p-typehole conducting paint. In some implementations, one or more additionallayers of the photosensitizing paint can be subsequently applied. Theone or more layers of photosensitizing paint can be subsequentlysintered. The sintering process for the one or more photosensitizingpaint layers is discussed in more detail below with reference to FIG. 8.

In some implementations, the photosensitizing paint layer includes asemiconductor paint layer and a photosensitized dye paint layer, wherethe semiconductor paint layer is applied to the p-type hole conductingpaint layer to yield a semiconductor paint layer in direct contact withthe layer of the p-type hole conducting paint, and the photosensitizeddye paint is applied to the semiconductor paint layer to yield aphotosensitized dye paint layer in direct contact with the semiconductorpaint layer. The semiconductor paint layer and photosensitized dye paintlayer combine to form a photosensitized paint layer, described in moredetail below with reference to FIG. 8.

In 606, n-type electron conducting paint is applied to thephotosensitizing paint layer and allowed to dry to yield a layer of then-type electron conducting paint in direct contact with the layer of thephotosensitizing paint layer. In some implementations, one or moreadditional layers of the n-type electron conducting paint can besubsequently applied. In some implementations, the one or more layers ofn-type electron conducting paint are subsequently sintered. Thesintering process for the one or more n-type electron conducting paintlayers is discussed in more detail below with reference to FIG. 9. Then-type electron conducting paint layer is typically transparent. In someimplementations, the p-type hole conducting layer is transparent inaddition to or in place of the n-type electron conducting layer beingtransparent.

In 608, a transparent protective paint is applied to the n-type electronconducting paint layer and allowed to dry to yield a layer of thetransparent protective paint in direct contact with the n-type electronconducting paint layer. In some implementations, one or more additionallayers of the transparent protective paint can be subsequently applied.The transparent protective paint can additionally be applied to exposedsurfaces of the solar paint circuit (e.g., solar paint circuit 100) suchthat the solar paint circuit is encapsulated within a transparentprotective coating.

FIG. 7 is a flow chart of an example process 700 for painting a p-typehole conducting paint layer (e.g., p-type hole conducting paint layer104). In one example, the p-type hole conducting paint includes p-typenanoparticles dispersed in solution. In 702, a layer of the p-typenanoparticles (e.g., copper oxide nanoparticles) dispersed in solution(e.g., denatured alcohol) are applied to a substrate (e.g., substrate102). Applying the p-type nanoparticles dispersed in solution may bedone using an atomizing sprayer or other aerosolized dispersingtechnique for evenly distributing the p-type nanoparticle solution ontothe substrate.

In 704, the solution of the p-type hole conducting paint is evaporated.In some implementations, the solution may be evaporated in ambientconditions. The substrate and/or a surface of the substrate may belocally heated (e.g., with a heat gun, infrared lamp, or other localizedheating source) as the p-type nanoparticle paint is applied to thesurface of the substrate in order to evaporate the solution (e.g.,solvent) or other fluid medium. A temperature of the localized heatingcan be selected based in part on the evaporation temperature of theparticular solution used in the p-type hole conducting paint (e.g., aboiling temperature of water or solvent).

In some implementations, multiple applications of the p-typenanoparticles dispersed in solution are applied and subsequently thesolution is evaporated to form multiple layers of the p-type holeconducting paint on the substrate. A number of applications of thep-type hole conducting paint onto the substrate may depend on a desiredthickness of the p-type hole conducting paint layer in a directionperpendicular to the surface of the substrate. The desired thickness maybe determined, for example, by cost of materials and/or a desired numberof charge carriers available for generation/recombination in the p-typehole conducting paint layer. In one example, multiple applications ofthe p-type hole conducting paint are applied such that the p-type holeconducting paint is several hundred microns thick in a directionperpendicular to the surface of the substrate.

In 706, the p-type hole conducting paint is sintered to form anelectrically continuous p-type hole conducting paint layer. A sinteringprocess may include heating the p-type hole conducting paint layer usinga furnace, a rapid thermal processing (RTP) system, or other heatingsource for a period of time until the p-type nanoparticles of the p-typehole conducting paint layers agglomerate into an electrically continuouslayer (e.g., as measured by a four-point probe or other resistancemeasurements), and/or a structurally continuous layer (e.g., as measuredby ellipsometry or other optical inspection). A range of combinations oftemperatures and durations for a sintering process may be appropriate toachieve an electrically continuous p-type hole conducting layer, and maydepend in part on a type of sintering process (e.g., a tool or system)used. In some implementations, a selected temperature and duration ofthe sintering process for the p-type hole conducting layer depends oncost-considerations, equipment limitations, and/or design limitations(e.g., thermal budget) of other paint layers in the solar paint circuit.

FIG. 8 is a flow chart of an example process 800 for painting aphotosensitized paint layer. In one example, a process for painting aphotosensitized paint layer includes a first step for painting a layerof semiconductor paint onto the p-type hole conducting paint layer and asecond step for painting a photosensitizer dye paint onto thesemiconductor paint layer.

In 802, a layer of semiconductor paint (e.g., semiconductornanoparticles dispersed in solution) is applied to the p-type holeconducting paint layer. The semiconductor nanoparticles can be, forexample, titanium dioxide nanoparticles that are dispersed in denaturedalcohol or deionized water and a surfactant (e.g., sodium dodecylsulfate).

Applying the semiconductor paint may be done using an atomizing sprayeror other aerosolized dispersing technique for evenly distributing thesemiconductor paint onto the p-type hole conducting paint layer.

In 804, the solution of the semiconductor paint layer is evaporated. Insome implementations, the solution (e.g., deionized water, denaturedalcohol, or another solvent) may be evaporated in ambient conditions.The p-type hole conducting layer, substrate, or both may be locallyheated (e.g., with a heat gun or other localized heating source) as thesemiconductor paint is applied to the surface of the p-type holeconducting layer in order to evaporate the solution (e.g., solvent orother fluid medium) of the semiconductor paint layer. A temperature ofthe localized heating can be selected based in part on the evaporationtemperature of the particular solution used in the semiconductorparticle paint (e.g., a boiling temperature of water or solvent).

In some implementations, multiple applications of the semiconductorpaint are applied and subsequently the solution medium (e.g., solvent)is evaporated to form multiple layers of the semiconducting paint on topof the p-type hole conducting paint layer. Multiple layers of thesemiconducting paint can be applied to the p-type hole conducting paintlayer until the semiconducting paint layer completely covers the p-typehole conducting paint layer in a uniform and continuous layer. In someimplementations, a number of semiconducting paint layers applied to thep-type hole conducting paint layer is selected to be the fewest possiblenumber of semiconductor paint layers while still forming an electricallycontinuous and/or structurally continuous film on top of the p-type holeconducting paint layer. A thickness of the p-type hole conducting paintlayer in a direction perpendicular to a surface of the substrate can bein the nanometer to micrometer range.

In 806, the semiconductor paint layer is sintered to form anelectrically continuous semiconductor paint layer. A sintering processmay include heating the semiconductor paint layer using a furnace, arapid thermal processing (RTP) system, or another heating source for aperiod of time until the semiconductor nanoparticles agglomerate into anelectrically continuous layer (e.g., as measured by a four-point probeor other resistance measurements). A range of combinations oftemperatures and durations for a sintering process may be appropriate toachieve an electrically continuous semiconductor paint layer, and maydepend in part on a type of sintering process (e.g., a tool or system)used. In some implementations, a selected temperature and duration ofthe sintering process for the semiconductor paint layer depends oncost-considerations, equipment limitations, and/or design limitations(e.g., thermal budget) of other paint layers in the solar paint circuit.

In 808, a photosensitized dye paint is applied to the semiconductorpaint layer. In some implementations, the photosensitized dye paintincludes a photosensitized dye (e.g., copper phthalocyanine) dispersedin solution (e.g., anhydrous ethanol or other denatured alcohol).

The photosensitized dye paint can be applied to the semiconductor paintlayer using an atomizing sprayer or other aerosolized dispersingtechnique for evenly distributing the photosensitized dye paint onto thesemiconductor paint layer. In some implementations, a particularaerosolized dispersing technique for applying the photosensitized dyepaint is selected to minimize a size of droplets of the paint during theapplication to the semiconductor paint layer.

In 810, the solution of the photosensitized dye paint layer isevaporated. In some implementations, the solution (e.g., deionizedwater, denatured alcohol, or another solvent) may be evaporated inambient conditions. The semiconductor paint layer, the p-type holeconducting paint layer, substrate, or a combination thereof may belocally heated (e.g., with a heat gun or other localized heating source)as the photosensitized dye paint is applied to the surface of thesemiconductor paint layer in order to evaporate the solvent or otherfluid medium of the photosensitized dye paint layer. A temperature ofthe localized heating can be selected based in part on the evaporationtemperature of the particular solution used in the photosensitized dyepaint (e.g., a boiling temperature of water or solvent).

In some implementations, multiple applications of the photosensitizeddye is applied to the semiconductor paint layer and subsequently thesolution medium (e.g., solvent) is evaporated to form multiple layers ofthe photosensitized dye paint on the semiconductor paint layer. In someimplementations, multiple layers of the photosensitized dye paint areapplied to the semiconductor paint layer until visual inspection of thephotosensitized dye paint layer appears blue-green in color. Other formsof optical and/or visual inspection of the layer are possible, forexample, using ellipsometry or a camera including machine-learning imagerecognition software.

In 812, the photosensitized dye paint layer is thermally processed(e.g., by thermal annealing, or by photonic curing) to chemisorb thephotosensitized dye paint layer onto the semiconductor paint layer(e.g., to chemisorb the phthalocyanine onto the titanium dioxidesurface) to form the photosensitized paint layer. A thermal treatmentprocess may include heating the semiconductor paint layer in a furnace,rapid thermal processing (RTP) system, pulsed light from a flashlamp, orother heating source for a period of time until the photosensitized dyeis chemisorbed onto the surface of the semiconductor paint layer. Thetemperature and duration of the thermal anneal may be selected such thatthe chemisorbed photosensitized dye is resistant to heat degradationunder the normal operating conditions of the solar paint circuit (e.g.,under ambient conditions including UV exposure). A range of combinationsof temperatures and durations for the thermal anneal may be appropriateto achieve a fully chemisorbed photosensitized dye layer, and may dependin part on a type of anneal process (e.g., a tool or system) used. Insome implementations, a selected temperature and duration of the thermalanneal for the photosensitized dye layer depends on cost-considerations,equipment limitations, and/or design limitations (e.g., thermal budget)of other paint layers in the solar paint circuit.

FIG. 9 is a flow chart of an example process 900 for painting an n-typeelectron conducting paint layer. In 902, a layer of n-type nanoparticles(e.g., aluminum-doped zinc oxide nanoparticles) dispersed in solution(e.g., a solvent) are applied to the photosensitized paint layer (e.g.,on a top surface of the photosensitized dye paint layer). Applying then-type nanoparticles dispersed in solution may be done using anatomizing sprayer or other aerosolized dispersing technique for evenlydistributing the n-type nanoparticle solution onto the photosensitizeddye paint layer.

In 904, the solution of the n-type electron conducting paint layer isevaporated. In some implementations, the solution may be evaporated inambient conditions. The photosensitized dye paint layer, thesemiconductor paint layer, the p-type hole conducting paint layer,substrate, or a combination thereof may be locally heated (e.g., with aheat gun, infrared lamp, or other localized heating source) as then-type nanoparticle paint is applied to the surface of thephotosensitized dye paint layer in order to evaporate the solution(e.g., solvent or other fluid medium). A temperature of the localizedheating can be selected based in part on the evaporation temperature ofthe particular solution used in the n-type electron conducting paint(e.g., a boiling temperature of water or solvent).

In some implementations, multiple applications of the n-type electronconducting paint are applied and subsequently the solution is evaporatedto form multiple layers of the n-type electron conducting paint on asurface of the photosensitized dye paint layer. In some implementations,multiple layers of the n-type electron conducting paint are applied tothe photosensitized dye paint layer until the transparency of the n-typeelectron conducting paint layer begins to decrease. The transparency ofthe n-type electron conducting paint layer may be determined, forexample, by visual inspection, ellipsometry, or a camera includingmachine-learning image recognition software. In some implementations,the transparency of the n-type electron conducting paint layer can bedetermined by measuring a conversion efficiency of a solar paint circuitincluding the n-type electron conducting paint layer (e.g., solar paintcircuit 100) and comparing it to a conversion efficiency of a known,well-performing solar cell (e.g., a commercially-available silicon solarcell).

In 906, the n-type electron conducting paint is sintered to form anelectrically continuous n-type electron conducting paint layer. Asintering process may include heating the n-type electron conductingpaint layer using a furnace, a rapid thermal processing (RTP) system, aninfrared lamp, or another heating source for a period of time until then-type nanoparticles agglomerate into an electrically continuous layer(e.g., as measured by a four-point probe or other resistancemeasurements) and/or a structurally continuous layer (e.g., asdetermined by ellipsometry or other form of optical inspection).Sintering conditions (e.g., temperature and duration) can be selected tominimize an amount of desorption of the photosensitized dye paint layerwhile still forming an electrically continuous n-type electronconducting paint layer. A range of combinations of temperatures anddurations for a sintering process may be appropriate to achieve anelectrically continuous n-type electron conducting layer, and may dependin part on a type of sintering process (e.g., a tool or system) used. Insome implementations, a selected temperature and duration of thesintering process for the n-type electron conducting layer depends oncost-considerations, equipment limitations, and/or design limitations(e.g., thermal budget) of other paint layers in the solar paint circuit.

In some implementations, the solar paint circuit (e.g., solar paintcircuit 100) is annealed after the n-type electron conducting paint isapplied and thermally processed (e.g., by photonic curing). Alow-temperature anneal (e.g., 145° C.) may be performed on the solarpainted circuit to mitigate migration or desorption of thephotosensitized dye paint layer (e.g., phthalocyanine) from thesemiconductor paint layer (e.g., titanium dioxide nanoparticle layer)during the fabrication process.

In some implementations, contacts are affixed to the top and bottom ofthe solar painted circuit (e.g., contact 112). Contacts may be fixed tothe solar painted circuit using a conductive glue, a conductive foilcoated with laminate, or the like. The two contacts can be selected eachof a different metal having a different work function (e.g., a steelcontact and a copper contact) such that the flow of electricity isdetermined by the respective work functions of the two contacts.

In some implementations, a transparent protective coating (e.g., plasticlaminate, polyurethane varnish) is applied to the exposed surfaces(e.g., a top surface of the n-type electron conducting layer) of thesolar painted circuit.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyfeatures or of what can be claimed, but rather as descriptions offeatures specific to particular embodiments of the described paintedcircuits and painted circuit elements. Though the painted circuits andpainted circuit elements examples are described herein as havingparticular layer structures, they should not be read as limiting. Forexample, the painted circuits and painted circuit elements are describedas operating in a “top-down” fashion where the devices are paintedlayer-by-layer such that the top layer is the top of the device. Whileprocesses are depicted in the drawings in a particular order, thisshould not be understood as requiring that such processes be performedin the particular order shown or in sequential order, or that allillustrated processes be performed, to achieve desirable results. Forexample, the painted circuits and painted circuit elements may also bepainted in a “bottom-up” fashion where the function of the devices isupside relative to their fabrication order. Additionally, “flip-chip”configurations can be imagined where two substrates are individuallypainted with paint layers and then combined.

Other complex painted circuit elements can be created using thetechniques and compositions described herein. For example, paintedantenna elements. Additionally, active matrices of multiple smallersub-elements (e.g., embedded painted circuit elements) can be createdusing the techniques and compositions described herein.

Thus, particular embodiments of the subject matter have been described.Other embodiments are within the scope of the following claims. In somecases, the actions recited in the claims can be performed in a differentorder and still achieve desirable results. In addition, the processesdepicted in the accompanying figures do not necessarily require theparticular order shown, or sequential order, to achieve desirableresults. In certain implementations, multitasking and parallelprocessing may be advantageous.

What is claimed is:
 1. A painted circuit, comprising: a substrate; andone or more paint layers applied to the substrate, wherein the one ormore paint layers each form an electrical component of the paintedcircuit, the one or more paint layers including: a p-type holeconducting paint layer applied to the substrate; a photosensitized paintlayer applied to the p-type hole conducting paint layer; an n-typeelectron conducting paint layer applied to the photosensitized paintlayer; and a transparent protective paint layer applied to the n-typeelectron conducting paint layer.
 2. The painted circuit of claim 1,wherein a given paint layer of the one or more paint layers comprises aconductive paint formulation having a resistance that is defined in partby a resistivity of a conductive material that is included in theconductive paint formulation and a thickness of the given paint layer,and wherein the resistance of the conductive paint formulation includinga conductive material having a higher resistivity provides a higherresistance than the resistance of the conductive paint formulationincluding a conductive material with a lower resistivity.
 3. The paintedcircuit of claim 1, wherein the p-type hole conducting paint layercomprises p-type nanoparticles.
 4. The painted circuit of claim 3,wherein the p-type nanoparticles are copper oxide nanoparticles.
 5. Thepainted circuit of claim 1, wherein the photosensitized paint layercomprises a semiconductor paint layer and a photosensitized dye paintlayer.
 6. The painted circuit of claim 5, wherein the semiconductorpaint layer comprises a titanium dioxide nanoparticles.
 7. The paintedcircuit of claim 5, wherein the photosensitized dye paint layercomprises copper phthalocyanine.
 8. The painted circuit of claim 1,wherein the n-type electron conducting paint layer comprises n-typenanoparticles.
 9. The painted circuit of claim 8, wherein the n-typenanoparticles are aluminum-doped zinc oxide nanoparticles.
 10. Thepainted circuit of claim 1, further comprising two or more contacts,each contact comprising a metallic foil affixed to a substrate or ann-type electron conducting paint layer and in electrical contact withthe substrate or the n-type electron conducting paint layer,respectively.
 11. A process for manufacturing a painted circuit,comprising: providing a substrate; and applying one or more paint layerson a surface of the substrate, the one or more paint layers each formingan electrical component of the painted circuit, wherein applying the oneor more paint layers includes: applying a p-type hole conducting paintto the substrate to yield a layer of the p-type hole conducting paint indirect contact with the substrate; applying a photosensitized paint tothe p-type hole conducting paint layer to yield a layer of thephotosensitized paint in direct contact with the p-type hole conductinglayer; applying an n-type electron conducting paint to thephotosensitized paint layer to yield a layer of the n-type electronconducting paint in direct contact with the photosensitized paint layer;and applying a transparent protective paint to the n-type electronconducting paint layer to yield a layer of the transparent protectivepaint in direct contact with the n-type electron conducting paint layer.12. The process of claim 11, wherein a given paint layer of the one ormore paint layers comprises a conductive paint formulation having aresistance that is defined in part by a resistivity of a conductivematerial that is included in the conductive paint formulation and athickness of the given paint layer, and wherein the resistance of theconductive paint formulation including a conductive material having ahigher resistivity provides a higher resistance than the resistance ofthe conductive paint formulation including a conductive material with alower resistivity.
 13. The process of claim 11, wherein applying ap-type hole conducting paint comprises applying a layer of p-typenanoparticles dispersed in solution on the substrate, and sintering thep-type nanoparticles to form an electrically continuous p-type holeconducting paint layer.
 14. The process of claim 13, wherein the p-typenanoparticles are copper oxide nanoparticles.
 15. The process of claim11, wherein applying a photosensitized paint comprises: applying a layerof semiconductor paint including semiconductor nanoparticles dispersedin solution on the p-type hole conducting paint layer; sintering thesemiconductor nanoparticles to form an electrically continuoussemiconductor paint layer; applying a layer of photosensitized dye paintto the semiconductor paint layer; and thermally processing thephotosensitized dye paint layer to chemisorb the photosensitized dyepaint layer onto the semiconductor paint layer.
 16. The process of claim15, wherein the semiconductor nanoparticles are titanium dioxidenanoparticles.
 17. The process of claim 15, wherein the photosensitizeddye is copper phthalocyanine in anhydrous ethanol.
 18. The process ofclaim 11, wherein applying an n-type electron conducting paint comprisesapplying a layer of n-type nanoparticles dispersed in solution on thephotosensitized paint layer, and sintering the n-type nanoparticles toform an electrically continuous n-type electron conducting paint layer.19. The process of claim 18, wherein the n-type nanoparticles arealuminum-doped zinc oxide nanoparticles.
 20. The process of claim 11,further comprising thermally processing the painted circuit.
 21. Theprocess of claim 11, further comprising affixing two or more contacts tothe painted circuit, wherein each contact comprises a metallic foil andis affixed to a substrate or an n-type electron conducting layer and inelectrical contact with the substrate or the n-type electron conductinglayer, respectively.